I also had a similar problem with the market a few hours after I updated [note, immediately after the update I was logged into the market]. Can you see that your GPRS, Edge, or 3G is doing any work? [the notification for it will light up if it is].

I solved this with a reboot. Why? No idea why this happened, and as long as it's a one-time thing for both you and me, I'm fine with not knowing.